The invention concerns a process for manufacturing fermented food products. More particularly, it relates to the use of the cell contents of micro-organisms in order to reduce the duration of the ripening phase and to improve the organoleptic properties of these products.
The processes for manufacturing fermented products may be divided into two major steps:
preparation of the product for fermentation,
ripening or maturation of this product, during which the constituents of the raw material are converted by the action of physical or biological factors, such as enzymes, certain of which are of microbial origin.
This second phase is often quite long. For obvious economic reasons, the use of different means has already been envisaged in order to shorten its duration. In the field of milk products, they consist of:
physical means: patent WO-A-8705470 describes the use of a magnetic field to accelerate the ripening of cheeses. Another patent recommends increasing the pressure;
microbiological means: certain patents describe the addition of particular micro-organisms in order to shorten the ripening period. Thus, patent EP 0 365 173 mentions the use of a novel micro-organism, while patents SU-A-1 353401 and NL-A-8700176 each refer to the addition of a particular lactobacillus with a normal lactococcus flora. Patent EP 0 304 119 describes the use of a concentrate obtained from fermentation products of components of cheese by the action of micro-organisms having a proteolytic, lipolytic or peptidolytic activity;
enzymatic means: certain patents describe the addition of an enzyme such as a protease, (EP 0 246 163), a fruit protease (JP-A-062661682), and a lipase extracted from a strain of Aspergillus (EP 0 167 309);
combination of means: certain processes envisage the addition to the raw material of an enzyme and a micro-organism in order to accelerate ripening. Patent CA 2 072 159 describes the use of a neutrase and a heated lactobacillus while patent EP 469 857 mentions the addition of a lactobacillus and a lipase or a protease.
The process described in patent EP 0 337 497 concerns the manufacture of fermented products and enables the maturation of these products to be accelerated by adding extracts of cells of one or more usual micro-organisms to the mass of raw material.
However, no proportions or indications are given as to the number of different types of micro-organisms making up the solution added to the raw material. Moreover, the examples, and more particularly example 2, emphasise that this process encourages the development of one or more flavours but does not deal with the ripening process in its entirety.
The description of the process made in this patent application thus does not indicate any technical means capable of resolving a problem in a reproducible manner.
The invention described in patent EP 0 058 856 concerns a process for the preparation of flavoured food products enabling the maturation time for the products to be reduced.
According to this invention, the flavouring and acceleration of the maturation process are brought about by the addition of an already fermented mass to the raw material and not by the direct addition of ripening factors. This mass is obtained by adding isolated enzyme complexes, derived from pure or mixed cultures of the usual micro-organisms, to a fraction of the material to be flavoured. The acceleration of ripening thus relies on the special treatment applied to this fraction.
Patent FR 2 368 224 claims the use of a purified protease extracted from a mould and an autolysate of the cells of a lactic bacterium as the proteolytic enzyme source.
Finally, patents U.S. Pat. No. 3,295,991 and EP 0 159 303 describe the addition to milk, after treatment, of an extract of micro-organisms normally used in the manufacture of cheese.
these extracts include one or more enzymes. Reading these two texts shows that:
these inventions relate to the addition of extracts having only a proteolytic action,
the extract mentioned is always produced from a very limited number of different micro-organism strains, which belong to the group of lactic bacteria.
It thus follows from a study of the prior art that:
many solutions have been envisaged for accelerating the ripening of fermented products;
these use different means;
if the means are microbiological, the micro-organism, or exceptionally micro-organisms, used are almost exclusively lactic bacteria;
if the means are enzymatic, it relates to a single enzyme family which is almost always that of proteases. Moreover, when the enzyme is derived from a micro-organism, this extract is partially or totally purified.
In the field of cured meat products, the processes used remain traditional and the acceleration of ripening has consequently not been studied.
Up to now, the solutions proposed to shorten the ripening phase of a fermented product using micro-organisms or their enzymes therefore aims almost solely at encouraging the biochemical processes brought about by lactic bacteria.
In addition, although the solutions of the prior art exhibit a certain efficiency as regards the shortening of the ripening phase, they still too often provide a final product having unsatisfactorily organoleptic properties. Indeed, whatever the acceleration process used, the product obtained generally exhibits an attenuation of flavours and unctuousness of the paste due to the attenuation of proteolysis or lipolysis. In order to compensate for this phenomenon, the tendency has been to modify the technology by increasing the fat content and to remove lactose during draining. The quality of the final product is however often very variable.
It should finally be noted that the manufacturing conditions (pH, temperature, duration of certain phases, addition of compounds etc.) for a given fermented food product are very strict. The biochemical reactions occurring during maturation are numerous, complex and sequential. Their combination is poorly understood and the intervention of a new factor, even an apparently simple one, in a ripening process always has consequences which are difficult to estimate.
The object of the present invention compared with the prior art is to shorten still further the ripening phase of fermented food products and to improve their organoleptic properties.
The present invention concerns a method for preparing and using the cell contents of a complete collection of micro-organisms for ripening fermented food products.
It more particularly concerns an improved process for manufacturing fermented food products such as cheeses or cured meat products by adding the cell contents of this collection to the components of the starting material.
In the normal process for manufacturing fermented products, the raw material is subjected to various treatments before the product is stored for ripening.
For a milk product, after standardization and if necessary heat treatment of the milk, the following stages are carried out, among others:
coagulation or precipitation of the curds; this is obtained by the addition of enzymes (rennet) or by acidification of the raw material; it may also be combined (rennet and acidifying compounds). To this stage of the process, according to the desired final product and the particular operating conditions, technological flora may be added (lactic ferment and/or ripening microbial flora, known as secondary flora).
draining: this separates the whey from the curds so as to bring the latter to a particular water content and so as to adjust mineralization. At the start of this phase, cutting and washing, stirring or furthermore pressing, washing and moulding may be carried out according to the final product desired.
salting: this acts on the bound water by changing the water bonds to the substrate. Accordingly, it completes draining, acts on the development of micro-organisms and consequently influences ripening and contributes to the flavour of the cheese,
ripening: this corresponds to the enzymatic digestion of the curds obtained by biochemical transformations, giving the cheese new properties; enzymes are ripening agents and have various origins (milk, rennet or rennet substitute, and micro-organisms from milk, from yeasts, from the atmosphere etc.).
It should be noted that the normal processes for manufacturing milk products do not systematically include the addition of a technological flora. Indeed, certain operating methods are such that the micro-organisms naturally present in milk or the contaminants coming from the environment in which this milk is collected and treated etc. are sufficient to ensure the desired conversion of these compounds of the raw material. The absence of seeding with any lactic or ripening flora thus does not signify that the cheese is manufactured without the intervention of this flora but that the latter is naturally present in the raw material.
For a cured meat products, the following are principally carried out:
cutting the meat,
adding additives and technological flora,
filling,
incubation,
storage for ripening.
These known processes have in common the use (natural presence or seeding) of a ripening flora consisting of a mixture of different micro-organisms (bacteria, yeasts and/or moulds) of which the nature and proportion are a function of the final product desired. This flora serves to transform the components of the raw material and to give the final product its characteristics of flavour and texture, etc. The quantity of cells thus added is generally between approximately 102 and 105 per milliliter of milk or gramme of meat according to the nature of the species. This quantity is less than that of living organisms taking part in the ripening mechanism. Indeed, the concentration of bacteria, yeasts and moulds varies with time by reason of their multiplication. The importance of this development varies according to the micro-organism considered, the conditions under which the treated raw material is kept, etc.
The invention consists of adding to the components of this raw material a collection of cell extracts taken from the collection of micro-organisms of which the composition and properties are based on those of the ripening flora, either natural or provided by seeding, for a given product.
The mixture of extracts of these multiple micro-organisms mainly contain proteases, peptidases, lipases and esterases, enzymes serving to catalyze the reactions which are poorly understood but which are however necessary for the maturation of these products, i.e. for conferring their characteristics of flavour, appearance and texture etc.
A cell equivalent is defined as all the constituents of this cell (cell contents and membrane fragments) after its lysis. According to the present invention, the number of cell equivalents forming the added collection is greater, by approximately 10 to 1000 times, than the number of cells constituting the ripening bacterial flora normally seeding the raw material. The collection of cell extracts thus ensures the provisions of 5.104 to 108 cell equivalents per milliliter of milk or gramme of meat.
The method for preparing the collection of extracts of micro-organisms comprises the steps of:
preparing the biomass;
optional concentration of this;
cell lysis;
blending the extracts obtained.
The living material is prepared by traditional fermentation carried out in such a way as to obtain a final biomass of approximately 109 ufc/ml for bacteria and 107 for yeasts and moulds. The micro-organisms used in this process are as follows:
GRAM+ Bacteria:
Corynebacteriaceae family:
genus Corynebacterium, of the species C. glutamicum 
genus Brevibacterium, of the species B. linens 
genus Arthrobacter, of the species A. globiformis 
genus Propionibacterium
Micrococaceae family:
genus Micrococcus
genus Staphylococcus, of the species S. xylosus and S. carnosus 
GRAMxe2x88x92 Bacteria:
Enterobacteriaceae family
genus Hafnia, of the species H. alvei 
genus Enterococcus, of the species E. faecalis or E. faecium 
Yeasts:
genus Debaryomyces, of the species D. hansenii 
genus Saccharomyces of the species S. cerevisiae 
genus Kluyveromyces, of the species K. lactis 
genus Geotrichum, of the species G. candidum 
Moulds:
Filamentous fungi family:
genus Penicillium, of the species P. candidum, P. chrysogenum, P. roquefortii and P. nalgiovensis 
The development of each strain used is carried out in separately. However certain related micro-organisms may be cultivated in the same fermenter.
Concentration of the biomass is an optional step. It is carried out by centrifuging, tangential filtration or any other method known in the art.
Cellular lysis is carried out by known means such as irradiation, heat treatment, freeze drying, ultra high pressures, osmotic shock, ultrasound, pH variations, grinding, enzyme treatment etc. It enables enzymes to be collected from bacteria, yeasts or moulds. It is chosen in such a way as to limit to a maximum the denaturing of these biological catalysts.
The blend of extracts of different origins, namely coming from each micro-organism cultivated, is prepared according to known processes. At this stage of the treatment, it is in the form of a suspension.
According to an alternative embodiment, this mixture is dried, frozen or treated by any process known in the art, giving it a solid form suitable for keeping.
The peculiarity of this collection is thus that it includes a relatively large number of enzymes. Each of these possesses a particular function (conversion of proteins, hydrolysis of peptides, modification of lipids and liberation of a large number of compounds, certain of which have an important part to play on the texture and flavour of the products). Their action, and that of the enzymes of ripening micro-organisms naturally present or incorporated, is accumulative.
This collection of the extracts of micro-organisms thus constitutes a complex factor for modifying the ripening process. It has been found however that it ensures that all the catalytic reactions are carried out which are necessary for good maturation while respecting the fermentation mechanisms which enable a final product to be obtained with a quality superior to that of a product obtained by a conventional process. Analyses making it possible to arrive at an assessment which is both objective, by instrumental methods (measurement of the concentration of organic acids), as well as subjective, by proving differences established by a jury of experts, show that this addition of a collection of extracts of micro-organisms also makes it possible to improve the organoleptic properties of the final product. With an equal ripening time, the products manufactured according to the process of the present invention compared with those obtained by the normal process, have an unchanged organic acid content and are judged to be better (score similar to a more intense flavour).
For a given product, the addition to its raw material of a mixture consisting of extracts of all or part of the micro-organisms taking part in its natural maturation therefore has the effect of accelerating its ripening and of improving its organoleptic properties.
The preferred method of use consists of adding the collection of extracts thus obtained to milk before coagulation during the introduction of rennet or acidifying compounds or to the meat blend before filling. The quantity of extract added depends on its method of preparation. For cultures producing the concentrations previously stated (109 for bacteria, 107 for years and moulds), it is approximately {fraction (1/10000)} of the volume (for milk) or of the mass (for meat) of the raw material if the biomass has been subjected to concentration steps and has been put into a salt solution. It is 1 % in the contrary case.
According to a variant, the collection of extracts of micro-organisms is incorporated in the raw material during its pretreatment i.e. 12 to 24 hours before the start of the manufacture.
According to another variant, this addition is made during a subsequent phase of the manufacturing process before maturation starts.
Table 1 gives a summary by family of the fermented food product, the preferred collection of micro-organisms and the number of cells, the extract of which is incorporated in 1 milliliter of milk or 1 gramme of meat.
According to one variant, the addition of this collection of cell extracts may be accompanied by one or more ripening factors consisting of enzymes, lactic bacteria, an extract from their cells and a collection of extracts from their cells or furthermore any other compatible treatment aimed at improving the process for manufacturing the fermented product.
According to another embodiment, the collection of extracts from micro-organisms is added in an excess compared with the proportions mentioned previously, to only a fraction of the raw material. The volume of this fraction is between 5 and 50 % of the volume or the mass of the raw material. After acceleration maturation due to the extent of the concentration of cell extracts, this fraction is itself added to the rest of the raw material. These two parts are mixed at any moment as long as they have consistencies which will ensure the uniformity of the said material. The addition of this fraction ripened in an accelerated manner mainly provides an addition of flavour.